1. H.Y. identification in mouse and fish. 2. Immune reactivity following syngeneic bone marrow transfusions. 3. Genetic analysis of abnormal hyperdiploid spleen cells of NZB mice. 4. Murine hemopoietic stem cells following bone marrow transfusions. 5. Sex reversal in fish. 6. Human cytogenetic studies of patients with congenital and developmental disorders as well as studies of mutagen-induced chromosomal abnormalities are continuing. 7. Application of differential staining techniques and continued improvement of established methods are basic to all of the projects conducted in the laboratory.